The amount of carbon that the Amazon rainforest is
absorbing from the atmosphere and storing each year has fallen by
around a third in the last decade, says a new 30-year study by
almost 100 researchers.
This decline in the Amazon carbon sink amounts
to one billion tonnes of carbon dioxide - equivalent to over twice
the UK's annual emissions, the researchers say.
If this pattern exists in other forests around
the world, deeper cuts in human-caused carbon dioxide emissions are
needed to meet climate targets, the researchers say.
Three billion trees
The Amazon rainforest is the largest rainforest
in the world. Spanning nine countries in South America, it's 25
times the size of the UK.
Using a process known as photosynthesis, the
Amazon's three billion trees convert carbon dioxide, water and
sunlight into the fuel they need to grow, locking up carbon in
their trunks and branches.
As they grow, Amazon trees account for a
quarter of the carbon dioxide absorbed by the land
Studies suggest that as human-caused carbon
dioxide emissions increase, forests will absorb and store more
carbon, assuming they have enough water and nutrients to
But a new study, published today in Nature
, suggests the Amazon has passed saturation point for how
much extra carbon it can take up.
Diminishing carbon sink
A team of almost 500 people monitored trees in
more than 300 sites across eight countries. Between 1983 and 2011,
the researchers measured the trees in each plot, recording the
number, size and density to calculate how much carbon each one
The trees took up more carbon and grew more
quickly during the 1990s, before levelling off since the year 2000.
You can see this in the middle chart below.